Embossed multi-ply fibrous structure product and process for making same

ABSTRACT

Multi-ply fibrous structure products, more specifically embossed multi-ply fibrous structure products and methods for making same are provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 10/673,659, filed Sep. 29, 2003.

FIELD OF THE INVENTION

The present invention relates to multi-ply fibrous structure products,more specifically embossed multi-ply fibrous structure products andmethods for making same.

BACKGROUND OF THE INVENTION

Conventional embossed multi-ply fibrous structure products havingembossment heights of 1000 μm or greater are known in the art. However,such conventional embossed multi-ply fibrous structure productscontained bonded, densified embossment sites. Such conventional embossedmulti-ply fibrous structure products exhibited product propertydeficiencies, especially with respect to the wet burst strength. Suchconventional embossed multi-ply fibrous structure products exhibited awet burst strength of 303 g or less. In addition, such conventionalembossed multi-ply fibrous structure products suffered from problemsassociated with the adhesive between the plies moving when embossedprior to achieving acceptable plybond strength. Tensile strengths insuch products were also typically lower than acceptable.

Prior art attempts to overcome the prior art's product propertydeficiencies included applying excess adhesive to the plies of thefibrous structure prior to embossing and then marrying the plies to forma multi-ply fibrous structure product. The adhesive covered greater than40% of the surface area of the plies. The relatively large amount ofadhesive was required to get acceptable plybond strength in the product.

Accordingly, there is a need for an embossed multi-ply fibrous structureproduct wherein the plies of the multi-ply fibrous structure productwere bonded together by an adhesive over less than 40% of the surfacearea of the plies. Further, there is a need for an embossed multi-plyfibrous structure product that comprises embossments having anembossment height of greater than 1000 μm and a wet burst strength of atleast 305 g and/or a plybond strength of at least 4 g/in.

SUMMARY OF THE INVENTION

The present invention fulfills the need described above by providing anembossed multi-ply fibrous structure product.

In one aspect of the present invention, an embossed multi-ply fibrousstructure product comprising two or more plies of fibrous structurebonded together along adjacent surfaces of the two or more plies by anadhesive to form a bond area, wherein the bond area is less than about30% of the bonded adjacent surfaces, wherein the product comprises twofaces, wherein one face comprises non-adhesively bonded embossed sitesand the other face comprises adhesively bonded non-embossed sites, andwherein the fibrous structure product exhibits an embossment height ofat least about 1000 μm, is provided.

In another aspect of the present invention, an embossed multi-plyfibrous structure product comprising two or more plies of fibrousstructure bonded together at a plybond strength of at least about 4 g/inalong adjacent surfaces of the two or more plies by an adhesive to forma bond area, wherein the bond area is less than about 30% of the bondedadjacent surfaces, wherein the product exhibits an embossment height ofat least about 1000 μm, and a wet burst of at least about 305 g, isprovided.

In still another aspect of the present invention, an embossed multi-plyfibrous structure product comprising a first face and a second face,wherein the first face comprises non-adhesively bonded embossed sitesand the second face comprises adhesively bonded non-embossed sites, isprovided.

In even another aspect of the present invention, an embossed multi-plyfibrous structure product comprising a first face and a second face,wherein the first face comprises non-densified embossed sites and thesecond face comprises densified non-embossed sites, is provided.

In yet another aspect of the present invention, a method for making anembossed multi-ply fibrous structure product comprising the steps of:

-   -   a) adhesively binding two or more plies of fibrous structure        together to form a multi-ply fibrous structure by applying an        adhesive to at least one surface of the two or more plies,        wherein the adhesive is applied to less than about 30% of at        least one of the two or more plies surfaces;    -   b) embossing the multi-ply fibrous structure such that the        multi-ply fibrous structure exhibits an embossment height of at        least about 1000 μm to form the embossed multi-ply fibrous        structure product, is provided.

In still yet another aspect of the present invention, a method formaking an embossed multi-ply fibrous structure product comprising thesteps of:

-   -   a) providing a first ply of fibrous structure;    -   b) providing a second ply of fibrous structure;    -   c) applying an adhesive to a surface of the first ply of fibrous        structure such that the adhesive contacts less than about 30% of        the surface area of the first ply of fibrous structure;    -   d) combining and marrying the first and second plies of fibrous        structure along adjacent surfaces of the first and second plies        of fibrous structure such that the adhesive bonds the two plies        together to form a multi-ply fibrous structure exhibiting a        plybond strength of at least about 4 g/in; and    -   e) embossing the multi-ply fibrous structure such that an        embossed multi-ply fibrous structure product exhibiting an        embossment height of at least 1000 μm is formed, is provided.

Accordingly, the present invention provides an embossed multi-plyfibrous structure product and methods for making embossed multi-plyfibrous structure products.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a fragmentary side sectional view of one embodiment of anembossed multi-ply fibrous structure product according to the presentinvention.

FIG. 1B is a fragmentary side sectional view of another embodiment of anembossed multi-ply fibrous structure product according to the presentinvention.

FIG. 1C is a fragmentary side sectional view of another embodiment of anembossed multi-ply fibrous structure product according to the presentinvention.

FIG. 2 is a schematic side elevational view of one embodiment of anapparatus used for making an embossed multi-ply fibrous structureproduct according to the present invention.

FIG. 3 is an enlarged fragmentary side elevational view of the apparatusshown in FIG. 2.

FIG. 4 is a top plan view of a fibrous structure comprising an adhesivein pattern form.

DETAILED DESCRIPTION OF THE INVENTION

“Fiber” as used herein means an elongate particulate having an apparentlength greatly exceeding its apparent width, i.e. a length to diameterratio of at least about 10. More specifically, as used herein, “fiber”refers to papermaking fibers. The present invention contemplates the useof a variety of papermaking fibers, such as, for example, natural fibersor synthetic fibers, or any other suitable fibers, and any combinationthereof. Papermaking fibers useful in the present invention includecellulosic fibers commonly known as wood pulp fibers. Applicable woodpulps include chemical pulps, such as Kraft, sulfite, and sulfate pulps,as well as mechanical pulps including, for example, groundwood,thermomechanical pulp and chemically modified thermomechanical pulp.Chemical pulps, however, may be preferred since they impart a superiortactile sense of softness to tissue sheets made therefrom. Pulps derivedfrom both deciduous trees (hereinafter, also referred to as “hardwood”)and coniferous trees (hereinafter, also referred to as “softwood”) maybe utilized. The hardwood and softwood fibers can be blended, oralternatively, can be deposited in layers to provide a stratified web.U.S. Pat. No. 4,300,981 and U.S. Pat. No. 3,994,771 are incorporatedherein by reference for the purpose of disclosing layering of hardwoodand softwood fibers. Also applicable to the present invention are fibersderived from recycled paper, which may contain any or all of the abovecategories as well as other non-fibrous materials such as fillers andadhesives used to facilitate the original papermaking. In addition tothe above, fibers and/or filaments made from polymers, specificallyhydroxyl polymers may be used in the present invention. Nonlimitingexamples of suitable hydroxyl polymers include polyvinyl alcohol,starch, starch derivatives, chitosan, chitosan derivatives, cellulosederivatives, gums, arabinans, galactans and mixtures thereof.

“Wet Burst Strength” as used herein is a measure of the ability of afibrous structure and/or a fibrous structure product incorporating afibrous structure to absorb energy, when wet and subjected todeformation normal to the plane of the fibrous structure and/or fibrousstructure product.

“Basis Weight” as used herein is the weight per unit area of a samplereported in lbs/3000 ft² or g/m². Basis weight is measured by preparingone or more samples of a certain area (m²) and weighing the sample(s) ofa fibrous structure according to the present invention and/or a fibrousstructure product comprising such fibrous structure on a top loadingbalance with a minimum resolution of 0.01 g. The balance is protectedfrom air drafts and other disturbances using a draft shield. Weights arerecorded when the readings on the balance become constant. The averageweight (g) is calculated and the average area of the samples (m²). Thebasis weight (g/m²) is calculated by dividing the average weight (g) bythe average area of the samples (m²).

“Machine Direction” or “MD” as used herein means the direction parallelto the flow of the fibrous structure through the papermaking machineand/or product manufacturing equipment.

“Cross Machine Direction” or “CD” as used herein means the directionperpendicular to the machine direction in the same plane of the fibrousstructure and/or fibrous structure product comprising the fibrousstructure.

“Sheet Caliper” or “Caliper” as used herein means the macroscopicthickness of a sample.

“Densified” as used herein means a portion of a fibrous structureproduct that exhibits a greater density than another portion of thefibrous structure product. For example, a densified area of the embossedmulti-ply fibrous structure product according to the present inventionis typically 0.19 g/cc or greater. In one embodiment of the presentinvention, the embossed multi-ply fibrous structure product comprises adensified area that is at least 2 times the density of another portionof the embossed multi-ply fibrous structure product.

“Non-densified” as used herein means a portion of a fibrous structureproduct that exhibits a lesser density than another portion of thefibrous structure product. For example, a non-densified area of theembossed multi-ply fibrous structure product according to the presentinvention is typically less than about 0.19 g/cc. In one embodiment ofthe present invention, the embossed multi-ply fibrous structure productcomprises a non-densified area that is less than 2 times the density ofanother portion of the embossed multi-ply fibrous structure product.

“Stretch” as used herein is determined by measuring a fibrousstructure's Dry Tensile Strength in MD and/or CD.

“Apparent Density” or “Density” as used herein means the basis weight ofa sample divided by the caliper with appropriate conversionsincorporated therein. Apparent density used herein has the units g/cm³(alternatively g/cc).

“Bulk Density” as used herein means the apparent density of an entirefibrous structure product rather than a discrete area thereof.

“Ply” or “Plies” as used herein means an individual fibrous structureoptionally to be disposed in a substantially contiguous, face-to-facerelationship with other plies, forming a multi-ply fibrous structure. Itis also contemplated that a single fibrous structure can effectivelyform two “plies” or multiple “plies”, for example, by being folded onitself.

Embossed Multi-ply Fibrous Structure Product

The embossed multi-ply fibrous structure product according to thepresent invention comprises two or more plies of fibrous structure thatare bonded together along their adjacent surfaces by an adhesive. Theadhesive may cover less than about 30% and/or from about 0.1% to about30% and/or from about 3% to about 30% and/or from about 5% to about 25%and/or from about 5% to about 20% of the bonded adjacent surfaces. Theadhesive may be applied to one or more of the plies of fibrous structurein a continuous and/or discontinuous network pattern, such as separate,discrete dots and/or separate, discrete stripes.

In one embodiment of the present invention, the embossed multi-plyfibrous structure exhibits a plybond strength of at least about 4 g/inand/or at least about 5 g/in and/or at least about 6 g/in as measured bythe Plybond Strength Test Method described herein.

In another embodiment of the present invention, the embossed multi-plyfibrous structure product comprises a first face and a second face,wherein the first face comprises non-adhesively bonded embossed sitesand the second face comprises adhesively bonded non-embossed sites.

In still another embodiment of the present invention, the embossedmulti-ply fibrous structure product comprises a first face and a secondface, wherein the first face comprises non-densified embossed sites andthe second face comprises densified non-embossed sites.

In even another embodiment of the present invention, the embossedmulti-ply fibrous structure product exhibits a wet burst strength of atleast 305 g and/or at least about 315 g and/or at least about 325 gand/or at least about 400 g as measured by the Wet Burst Strength TestMethod as described herein.

In yet another embodiment of the present invention, the embossedmulti-ply fibrous structure product comprises embossed sites of at least1000 μm and/or from about 1000 μm to about 5000 μm and/or from about1100 μm to about 3000 μm and/or from about 1100 μm to about 2000 μm asmeasured by the Embossment Height Test Method described herein.

In even another embodiment of the present invention, the embossedmulti-ply fibrous structure product comprises densified andnon-densified regions wherein the densified regions exhibit a caliper of10 mils or less and/or from about 0.1 to about 6 mils and/or from about1 to about 5 mils.

In still yet another embodiment of the present invention, the embossedmulti-ply fibrous structure product wherein the product exhibits a sheetcaliper of at least about 30 mils and/or at least about 40 mils and/orat least about 50 mils as measured by the Sheet Caliper Test Method.

In even yet another embodiment of the present invention, the embossedmulti-ply fibrous structure product exhibits a sheet caliper toeffective caliper ratio of greater than 1.1 and/or greater than 1.2and/or greater than 1.3.

In even still another embodiment of the present invention, the embossedmulti-ply fibrous structure product exhibits a cross machine directionstretch at peak load of greater than about 8% and/or greater than about10% and/or greater than about 12% as measured by the Stretch Test Methoddescribed herein.

The embossed multi-ply fibrous structure product may be in roll form.When in roll form, the embossed multi-ply fibrous structure product maybe convolutely wound about a core or may be convolutely wound without acore.

The embossed multi-ply fibrous structure product may have a basis weightof between about 10 g/m² and about 120 g/m², and bulk density of about0.10 g/cc or less. Preferably, the basis weight will be below about 60g/m²; and the bulk density will be about 0.07 g/cc or less. Mostpreferably, the bulk density will be between about 0.02 g/cc and about0.07 g/cc as measured by the Basis Weight Method described herein.

The embossed multi-ply fibrous structure product may comprise coloringagents, such as print elements.

A nonlimiting example of an embossed multi-ply fibrous structure productin accordance with the present invention is shown in FIG. 1A. As shownin FIG. 1A, the embossed multi-ply fibrous structure product 10comprises a first ply of fibrous structure 12 and a second ply offibrous structure 14 that are adhesively bonded together by an adhesivealong their adjacent surfaces 16 and 18, respectively at bond sites 20.The embossed multi-ply fibrous structure product 10 further comprisesembossment sites 22. The embossment sites 22 exhibit an embossmentheight a of at least 1000 μm. The embossment sites 22 extend in they-direction from the x-plane of the embossed multi-ply fibrous structureproduct 10. The embossment sites are not adhesively bonded together andare not densified. The bond sites 20 are adhesively bonded together byadhesive 24 and are densified.

Further, the embossed multi-ply fibrous structure product 10 as shown inFIG. 1A comprises a first face 52 and a second face 54.

Another embodiment of an embossed multi-ply fibrous structure product inaccordance with the present invention is shown in FIG. 1B. As shown inFIG. 1B, the embossed multi-ply fibrous structure product 10 comprises afirst ply of fibrous structure 12 and a second ply of fibrous structure14 that are adhesively bonded together by an adhesive along theiradjacent surfaces 16 and 18, respectively at bond sites 20. The embossedmulti-ply fibrous structure product 10 further comprises embossmentsites 22. The embossment sites 22 exhibit an embossment height a of atleast 1000 μm. The embossment sites 22 extend in the y-direction fromthe x-plane of the embossed multi-ply fibrous structure product 10. Theembossment sites are not adhesively bonded together and are notdensified. The bond sites 20 are adhesively bonded together by adhesive24 and are densified and plybond strength is maintained.

Further, the embossed multi-ply fibrous structure product 10 as shown inFIG. 1B comprises a first face 52 and a second face 54.

Another embodiment of an embossed multi-ply fibrous structure product inaccordance with the present invention is shown in FIG. 1C. As shown inFIG. 1C, the embossed multi-ply fibrous structure product 10 comprises afirst ply of fibrous structure 12 and a second ply of fibrous structure14 that are adhesively bonded together by an adhesive along theiradjacent surfaces 16 and 18, respectively at bond sites 20. The embossedmulti-ply fibrous structure product 10 further comprises embossmentsites 22. The embossment sites 22 exhibit an embossment height a of atleast 1000 μm. The embossment sites 22 extend in the y-direction fromthe x-plane of the embossed multi-ply fibrous structure product 10. Theembossment sites are not adhesively bonded together and are notdensified. The bond sites 20 are adhesively bonded together by adhesive24 and are densified and plybond strength is maintained.

Further, the embossed multi-ply fibrous structure product 10 as shown inFIG. 1C comprises a first face 52 and a second face 54.

The embossed multi-ply fibrous structure product 10 as shown in FIGS. 1Band 1C may have been designed to look identical to the embossedmulti-ply fibrous structure product 10 as shown in FIG. 1A. However,during the embossing step of the method of making the product, the bondsites 20 of the multi-ply fibrous structure from which the product 10derives may shift relative to the embossment sites 22.

Fibrous Structure

The embossed multi-ply fibrous structure product in accordance with thepresent invention may comprise a ply of fibrous structure selected fromthe group consisting of: through-air-dried fibrous structure plies,differential density fibrous structure plies, wet laid fibrous structureplies, air laid fibrous structure plies, conventional fibrous structureplies and mixtures thereof. The embossed multi-ply fibrous structureproduct may comprise identical types of plies or mixtures of differenttypes of plies.

The fibrous structure may be foreshortened by creping and/or by wetmicrocontraction and/or by rush transferring. Alternatively, the fibrousstructure may not be foreshortened.

The fibrous structure may be pattern densified. A pattern densifiedfibrous structure is characterized by having a relatively high-bulkfield of relatively low fiber density and an array of densified zones ofrelatively high fiber density. The high-bulk field is alternativelycharacterized as a field of pillow regions. The densified zones arealternatively referred to as knuckle regions. The densified zones may bediscretely spaced within the high-bulk field or may be interconnected,either fully or partially, within the high-bulk field. A preferredmethod of making a pattern densified fibrous structure and devices usedtherein are described in U.S. Pat. Nos. 4,529,480 and 4,528,239.

The fibrous structure may be uncompacted, non pattern-densified.

The fibrous structure may be of a homogenous or multilayeredconstruction.

The fibrous structure may be made with a fibrous furnish that produces asingle layer embryonic fibrous web or a fibrous furnish that produces amulti-layer embryonic fibrous web.

Ingredients

The fibrous structures and/or embossed multi-ply fibrous structureproduct made therefrom may comprise one or more ingredients, such assoftening agents, absorbency agents such as surfactants, wet strengthagents, lotions, antibacterial agents, coloring agents, perfumes.

Methods for Making Embossed Multi-ply Fibrous Structure Product

The embossed multi-ply fibrous structure product of the presentinvention may be made by the following nonlimiting example.

As shown in FIGS. 2 and 3, a first ply of fibrous structure 12 contactsknob surfaces 42 of a first embossing roll 26, such as an engraved steelembossing roll. An applicator roll 28 for applying an adhesive 24applies the adhesive 24 to the first ply of fibrous structure 12 wherethe fibrous structure ply 12 is supported by the knob surfaces 42. Theadhesive 24 may be applied to the fibrous structure ply 12 in a patternof discrete dots 50 to produce an adhesive-containing fibrous structure12′ as shown in FIG. 4. The adhesive 24 may be applied to the applicatorroll 28 by a gravure system, preferably an offset gravure systemcomprising a gravure roll 30. The gravure system can meter a specifiedamount of adhesive 24 from an adhesive pan (not shown) onto theapplicator roll 28. Other suitable means of applying the adhesive 24 areknown to those of ordinary skill in the art. The adhesive 24 may be anysuitable adhesive known in the art. Preferably, the adhesive 24comprises polyvinyl alcohol.

The first ply of fibrous structure 12 may be under tension suitable forcontrolling the first ply at some point during its contact with thefirst embossing roll 26.

A second ply of fibrous structure 14 is brought into contact with theadhesive 24 present on the first ply of fibrous structure 12′ at a nipbetween the first embossing roll 26 and a marrying roll 32. The firstply and second ply are bonded together (i.e., combined) into a multi-plyfibrous structure 48. The marrying roll 32 may be a solid marrying roll,i.e., smooth surface marrying roll.

The marrying roll 32 applies pressure to the multi-ply fibrous structure48 and the adhesive 24 is pressed between the two plies of fibrousstructure at the bond sites 20 where the first ply of fibrous structure12′ is supported by knob surfaces 42. This action bonds the two pliestogether and produces a plybond strength of at least about 4 g/in. Atthis point, the multi-ply fibrous structure 48 has not yet beenembossed.

Next, the multi-ply fibrous structure 48 enters the interface betweenthe first embossing roll 26 with its depressions 44 and a secondembossing roll 34 with its protuberances 46. The second embossing roll34 may be a steel embossing roll. The protuberances 46 of the secondembossing roll 34 and the depressions 44 of the first embossing roll 26are aligned such that the protuberances 46 nest within the depressions44. The protuberances 46 are engaged into the depressions 44 at a lengthof at least about 50 mils such that an embossed height of at least 1000μm is formed in the multi-ply fibrous structure 48. The embossedmulti-ply fibrous structure 10 product exits the nip between the firstembossing roll 26 and the second embossing roll 34.

The bond sites 20 are densified at the nip between the first embossingroll 26 and the marrying roll 32 and/or at the interface between thefirst embossing roll 26 and the second embossing roll 34.

The embossment sites 16 which result from the protuberances 46 of thesecond embossing roll 34 engaging the depressions 44 of the firstembossing roll 26 are non-densified.

Web handling rolls 36, 38 and 40 may be used to control and/or advancethe fibrous structures 12 and 14 and/or multi-ply fibrous structureproduct 10.

Preferred rotational direction of the rolls used in this method arerepresented by arrows associated with the rolls.

It is desirable that rolls 26, 28, 32 and 34 run at the same speed. Webhandling rolls 36, 38 and 40 do not have to run at the same speed asrolls 26, 28, 32 and 34.

Preferred machine direction of the fibrous structures 12 and 14 and/ormulti-ply fibrous structure product 10 are represented by arrowsassociated with the fibrous structures 12 and 14 and/or multi-plyfibrous structure product 10.

Test Methods:

Effective Caliper Test

Effective caliper of a fibrous structure in roll form is determined bythe following equation:EC=(RD ² −CD ²)/(0.00127×SC×SL)wherein EC is effective caliper in mils of a single sheet in a woundroll of fibrous structure; RD is roll diameter in inches; CD is corediameter in inches; SC is sheet count; and SL is sheet length in inches.Plybond Strength Test Method

Plybond strength is measured according to the following test method.

From a single multi-ply fibrous structure comprising an adhesive thatbonds two or more of the plies together cut four (4) 3″×8.2″ (76.2mm×208.3 mm) continuous (i.e., non-perforated) fibrous structure samplestrips conditioned with all wrapping and/or packaging materials removed,if necessary, at a temperature of 73° F.±2° F. (about 23° C.±1° C.) anda relative humidity of 50%±2% for two (2) hours. This test methodmeasures the plybond strength between two adjacent plies of the fibrousstructure.

The fibrous structure sample strips are prepared by using a cutting die[3″×11″(76.2 mm×279.4 mm)] on a plywood base, commercially availablefrom Acme Steel Rule Corp., 5 Stevens St., Waterbury, Conn. 06714. Thecutting die must be modified with a soft foam rubber insert material. AJDC Cutter 3″ (76.2 mm), Model #JDC-3-12 Precision Sample Cutter,Thwing-Albert Instrument Company, 10960 Dutton Road, Philadelphia, Pa.19154, having a side capacity to cut 3″×8.2″ (76.2 mm×208.3 mm) fibrousstructure sample strips is used to cut the fibrous structure samples.The 3″ (76.2 mm) wide strip are cut from the center of the fibrousstructure. The strips are cut in the MD direction of the fibrousstructure. If the fibrous structure is in roll form, cut the samplesfrom greater than 40″ (1016 mm) from the ends of the roll.

Individually take each sample strip and gently manually initiate plyseparation along the MD direction and continuing for 2″ (50 mm).

Do not use samples that contain obvious defects, such as wrinkles,creases, tears, holes, etc.

The measuring of the samples and the preparation of the samples shouldall occur in a conditioned environment at a temperature of 73° F.±2° F.(about 23° C.±1° C.) and a relative humidity of 50%±2%.

A Thwing-Albert EJA or Intelect-II-STD, Cat. No. 1451-24PG;Thwing-Albert Instrument Company tensile tester is used to measure theplybond strength of the samples. The tensile tester has general purposeair-operated grips (Cat. No. 734K) with 1″×3″ (25.4 mm×76.2 mm) inserts.The load cell of the tensile tester is 5000 g. The Sample Size Setting(Load Divider) is set to 3. The tensile tester is operated as follows:

-   -   1. Place one of the separated plies of the prepared sample strip        in the top grid of the tensile tester. The other ply is placed        in the bottom grid. The sample strip needs to be centered in the        grips and straight.    -   2. Activate the tensile tester. When the test is complete,        record the value for the load mean. Remove the sample strip from        the grips and discard. Check the load cell for a zero reading.    -   3. Repeat steps 1 and 2 for each sample strip.

The tensile tester will display a value for load mean in g/in (g/25.4mm). Take the average of four (4) sample strips to obtain the plybondstrength of the fibrous structure.

Bond Area Test Method

Bond area is a measurement that a manufacturer of a fibrous structureknows before the fibrous structure is produced. It represents thesurface area of adjacent surfaces of two or more plies of fibrousstructure that are bonded together by an adhesive. Most typically, theadhesive is applied only to the tips of the embossing knobs of anembossing roll. This area is known from the manufacturer of theembossing rolls, from which the manufacturer of the fibrous structurecan obtain such bond area measurement.

Additionally, the bond area can be measured by taking a sample offibrous structure that comprises an adhesive comprising polyvinylalcohol as the only adhesive, rather than a non-polyvinylalcohol-containing adhesive. Accordingly, if a fibrous structuretypically is made with a non-polyvinyl alcohol-containing adhesive, themaker of such a fibrous structure will need to replace its non-polyvinylalcohol-containing adhesive with an adhesive comprising polyvinylalcohol. The maker will then produce its fibrous structure in theidentical manner as it does when making its non-polyvinylalcohol-containing fibrous structure.

Next, the sample of fibrous structure comprising the adhesive comprisingpolyvinyl alcohol is subjected to an 8:1 ratio by volume of boric acidsolution to iodine solution mixture. The boric acid solution is a 4%boric acid solution in deionized water. The iodine solution is a 0.1 Niodine solution in deionized water. The mixture is sprayed onto thesample. The polyvinyl alcohol in the adhesive will turn bluish green.The resulting image can be analyzed for % bond area (i.e., adhesive areacoverage) using standard image analysis techniques.

Also, the bond area of a sample of fibrous structure that comprises anon-polyvinyl alcohol-containing adhesive as the only adhesive can bemeasured by subjecting such a sample to a method that identifies thearea of the fibrous structure sample that comprises the non-polyvinylalcohol-containing adhesive. For example, by subjecting the fibrousstructure sample to a condition, such as a chemical agent, thatcolorizes the non-polyvinyl alcohol-containing adhesive making itreadily visible for image analysis techniques. Another example includessubjecting the fibrous structure sample to a condition, such as achemical agent, that colorizes everything but the non-polyvinylalcohol-containing adhesive making the adhesive readily visible forimage analysis techniques.

If any one of these techniques identifies a fibrous structure sample ascomprising a bond area of from about 0.1% to about 30% of the surfacearea of the adjacent surfaces of the two or more plies, then the fibrousstructure satisfies the bond area aspect of the present invention.

Embossment Height Test Method

Embossment height is measured using a GFM Primos Optical Profilerinstrument commercially available from GFMesstechnik GmbH, Warthestraβe21, D14513 Teltow/Berlin, Germany. The GFM Primos Optical Profilerinstrument includes a compact optical measuring sensor based on thedigital micro mirror projection, consisting of the following maincomponents: a) DMD projector with 1024×768 direct digital controlledmicro mirrors, b) CCD camera with high resolution (1300×1000 pixels), c)projection optics adapted to a measuring area of at least 27×22 mm, andd) recording optics adapted to a measuring area of at least 27×22 mm; atable tripod based on a small hard stone plate; a cold light source; ameasuring, control, and evaluation computer; measuring, control, andevaluation software ODSCAD 4.0, English version; and adjusting probesfor lateral (x-y) and vertical (z) calibration.

The GFM Primos Optical Profiler system measures the surface height of asample using the digital micro-mirror pattern projection technique. Theresult of the analysis is a map of surface height (z) vs. xydisplacement. The system has a field of view of 27×22 mm with aresolution of 21 microns. The height resolution should be set to between0.10 and 1.00 micron. The height range is 64,000 times the resolution.

To measure a fibrous structure sample do the following:

-   -   1. Turn on the cold light source. The settings on the cold light        source should be 4 and C, which should give a reading of 3000K        on the display;    -   2. Turn on the computer, monitor and printer and open the ODSCAD        4.0 Primos Software.    -   3. Select “Start Measurement” icon from the Primos taskbar and        then click the “Live Pic” button.    -   4. Place a 30 mm by 30 mm sample of fibrous structure product        conditioned at a temperature of 73° F.±2° F. (about 23° C.±1°        C.) and a relative humidity of 50%±2% under the projection head        and adjust the distance for best focus.    -   5. Click the “Pattern” button repeatedly to project one of        several focusing patterns to aid in achieving the best focus        (the software cross hair should align with the projected cross        hair when optimal focus is achieved). Position the projection        head to be normal to the sample surface.    -   6. Adjust image brightness by changing the aperture on the lens        through the hole in the side of the projector head and/or        altering the camera “gain” setting on the screen. Do not set the        gain higher than 7 to control the amount of electronic noise.        When the illumination is optimum, the red circle at bottom of        the screen labeled “I.O.” will turn green.    -   7. Select Technical Surface/Rough measurement type.    -   8. Click on the “Measure” button. This will freeze on the live        image on the screen and, simultaneously, the image will be        captured and digitized. It is important to keep the sample still        during this time to avoid blurring of the captured image. The        image will be captured in approximately 20 seconds.    -   9. If the image is satisfactory, save the image to a computer        file with “.omc” extension. This will also save the camera image        file “.kam”.    -   10. To move the date into the analysis portion of the software,        click on the clipboard/man icon.    -   11. Now, click on the icon “Draw Cutting Lines”. Make sure        active line is set to line 1. Move the cross hairs to the lowest        point on the left side of the computer screen image and click        the mouse. Then move the cross hairs to the lowest point on the        right side of the computer screen image on the current line and        click the mouse. Now click on “Align” by marked points icon. Now        click the mouse on the lowest point on this line, and then click        the mouse on the highest point on this line. Click the        “Vertical” distance icon. Record the distance measurement. Now        increase the active line to the next line, and repeat the        previous steps, do this until all lines have been measured        (six (6) lines in total. Take the average of all recorded        numbers, and if the units is not micrometers, convert it to        micrometers (μm). This number is the embossment height. Repeat        this procedure for another image in the fibrous structure        product sample and take the average of the embossment heights.        Wet Burst Strength Test Method

Wet burst strength may be measured using a Thwing-Albert Burst TesterCat. No. 177 equipped with a 2000 g load cell commercially availablefrom Thwing-Albert Instrument Company, Philadelphia, Pa.

Wet burst strength is measured by taking two (2) multi-ply fibrousstructure product samples. Using scissors, cut the samples in half inthe MD so that they are approximately 228 mm in the machine directionand approximately 114 mm in the cross machine direction, each two (2)plies thick (you now have 4 samples). First, condition the samples fortwo (2) hours at a temperature of 73° F.±2° F. (about 23° C.±1° C.) anda relative humidity of 50%±2%. Next age the samples by stacking thesamples together with a small paper clip and “fan” the other end of thestack of samples by a clamp in a 105° C. (±1° C.) forced draft oven for5 minutes (±10 seconds). After the heating period, remove the samplestack from the oven and cool for a minimum of three (3) minutes beforetesting. Take one sample strip, holding the sample by the narrow crossmachine direction edges, dipping the center of the sample into a panfilled with about 25 mm of distilled water. Leave the sample in thewater four (4) (±0.5) seconds. Remove and drain for three (3) (±0.5)seconds holding the sample so the water runs off in the cross machinedirection. Proceed with the test immediately after the drain step. Placethe wet sample on the lower ring of a sample holding device of the BurstTester with the outer surface of the sample facing up so that the wetpart of the sample completely covers the open surface of the sampleholding ring. If wrinkles are present, discard the samples and repeatwith a new sample. After the sample is properly in place on the lowersample holding ring, turn the switch that lowers the upper ring on theBurst Tester. The sample to be tested is now securely gripped in thesample holding unit. Start the burst test immediately at this point bypressing the start button on the Burst Tester. A plunger will begin torise toward the wet surface of the sample. At the point when the sampletears or ruptures, report the maximum reading. The plunger willautomatically reverse and return to its original starting position.Repeat this procedure on three (3) more samples for a total of four (4)tests, i.e., four (4) replicates. Report the results as an average ofthe four (4) replicates, to the nearest g.

Sheet Caliper Test Method

Sheet Caliper or Caliper of a sample of fibrous structure product isdetermined by cutting a sample of the fibrous structure product suchthat it is larger in size than a load foot loading surface where theload foot loading surface has a circular surface area of about 3.14 in².The sample is confined between a horizontal flat surface and the loadfoot loading surface. The load foot loading surface applies a confiningpressure to the sample of 14.7 g/cm² (about 0.21 psi). The caliper isthe resulting gap between the flat surface and the load foot loadingsurface. Such measurements can be obtained on a VIR Electronic ThicknessTester Model II available from Thwing-Albert Instrument Company,Philadelphia, Pa. The caliper measurement is repeated and recorded atleast five (5) times so that an average caliper can be calculated. Theresult is reported in mils.

Stretch Test Method

Stretch is measured by providing one (1) inch by five (5) inch (2.5cm×12.7 cm) strips of fibrous structure. Each strip is placed on anelectronic tensile tester Model 1122 commercially available from InstronCorp., Canton, Mass. in a conditioned room at a temperature of 73° F.±2°F. (about 23° C.±1° C.) and a relative humidity of 50%±2%. The crossheadspeed of the tensile tester is 2.0 inches per minute (about 5.1cm/minute) and the gauge length is 4.0 inches (about 10.2 cm). TheStretch at Peak Load is measured.

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated by reference herein; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention. To the extent that any meaning ordefinition of the term in this written document conflicts with anymeaning or definition of the term in a document incorporated byreference, the meaning or definition assigned to the term in thiswritten document shall govern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A method for making an embossed multi-ply fibrous structure productcomprising the steps of: a) adhesively binding two or more plies offibrous structure together to form a multi-ply fibrous structure byapplying an adhesive to at least one surface of the two or more plies,wherein the adhesive is applied to less than about 30% of at least oneof the two or more plies surfaces; b) embossing the multi-ply fibrousstructure such that the multi-ply fibrous structure exhibits anembossment height of at least about 1000 μm to form the embossedmulti-ply fibrous structure product.
 2. The method according to claim 1wherein the adhesive is applied in an amount sufficient to provide aplybond strength of at least 4 g/in in the embossed multi-ply fibrousstructure product.
 3. The method according to claim 1 wherein at leastone of the two or more plies of fibrous structure comprises a fibrousstructure selected from the group consisting of: through-air-driedfibrous structure plies, differential density fibrous structure plies,wet laid fibrous structure plies, air laid fibrous structure plies,conventional fibrous structure plies and mixtures thereof
 4. The methodaccording to claim 1 wherein the multi-ply embossed fibrous structureproduct exhibits a wet burst of at least about 305 g.
 5. The methodaccording to claim 1 wherein the adhesive is applied to the adjacentsurfaces in the form of separate, discrete dots and/or separate,discrete stripes.
 6. A method for making an embossed multi-ply fibrousstructure product comprising the steps of: a) providing a first ply offibrous structure; b) providing a second ply of fibrous structure; c)applying an adhesive to a surface of the first ply of fibrous structuresuch that the adhesive contacts from about 0.1% to about 30% of thesurface area of the first ply of fibrous structure; d) combining andmarrying the first and second plies of fibrous structure along adjacentsurfaces of the first and second plies of fibrous structure such thatthe adhesive bonds the two plies together to form a multi-ply fibrousstructure exhibiting a plybond strength of at least about 4 g/in; and e)embossing the multi-ply fibrous structure such that an embossedmulti-ply fibrous structure product exhibiting an embossment height ofat least 1000 μm is formed.